Tissue damage, evaluated as the size of the hole left by the needle after retraction, bleeding, and tissue fracturing, was found to increase for increasing insertion speeds and was higher within white matter regions.

A statistically significant difference in hole areas with respect to insertion speed was found.

While there are no previous needle insertion speed studies with which to directly compare, previous electrode insertion studies have noted greater brain surface dimpling and insertion forces with increasing insertion speed [43–45]. These higher deformation and force measures may indicate greater brain tissue damage which is in agreement with the present study.

There are also studies which have found that fast insertion of sharp tip electrodes produced less blood vessel rupture and bleeding [28,29].

These differences in rate dependent damage may be due to differences in tip geometry (diameter and tip) or tissue region, since these electrode studies focus mainly on the cortex [28,29].

In the present study, hole measurements were small in the cortex, and no substantial bleeding was observed in the cortex except when it was produced during dura mater removal.

Any hemorrhage was observed primarily in white matter regions of the external capsule and the CPu.